/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

/**
 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
 * but null values are. An {@code EnumHashBiMap} and its inverse are both
 * serializable.
 * 
 * @author Mike Bostock
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
public final class EnumHashBiMap<K extends Enum<K>, V> extends
        AbstractBiMap<K, V> {
    private transient Class<K> keyType;

    /**
     * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
     * 
     * @param keyType
     *            the key type
     */
    public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(
            Class<K> keyType) {
        return new EnumHashBiMap<K, V>(keyType);
    }

    /**
     * Constructs a new bimap with the same mappings as the specified map. If
     * the specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap},
     * the new bimap has the same key type as the input bimap. Otherwise, the
     * specified map must contain at least one mapping, in order to determine
     * the key type.
     * 
     * @param map
     *            the map whose mappings are to be placed in this map
     * @throws IllegalArgumentException
     *             if map is not an {@code EnumBiMap} or an
     *             {@code EnumHashBiMap} instance and contains no mappings
     */
    public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(
            Map<K, ? extends V> map) {
        EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
        bimap.putAll(map);
        return bimap;
    }

    private EnumHashBiMap(Class<K> keyType) {
        super(new EnumMap<K, V>(keyType),
                Maps.<V, K> newHashMapWithExpectedSize(keyType
                        .getEnumConstants().length));
        this.keyType = keyType;
    }

    // Overriding these two methods to show that values may be null (but not
    // keys)

    @Override
    public V put(K key, @Nullable V value) {
        return super.put(key, value);
    }

    @Override
    public V forcePut(K key, @Nullable V value) {
        return super.forcePut(key, value);
    }

    /** Returns the associated key type. */
    public Class<K> keyType() {
        return keyType;
    }

    /**
     * @serialData the key class, number of entries, first key, first value,
     *             second key, second value, and so on.
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(keyType);
        Serialization.writeMap(this, stream);
    }

    @SuppressWarnings("unchecked")
    // reading field populated by writeObject
    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        keyType = (Class<K>) stream.readObject();
        setDelegates(new EnumMap<K, V>(keyType),
                new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
        Serialization.populateMap(this, stream);
    }

    private static final long serialVersionUID = 0;
}
